Which phenomenon refers to changes in a subject's performance when they are aware they are participating in research?

The Hawthorne Effect is the phenomenon that describes changes in a subject's performance due to their awareness of being observed or participating in research. This effect stems from the fact that individuals may alter their behavior based on the perception that they are part of a study or being monitored, which can lead to improved performance or other changes that would not occur in a more natural setting.

This phenomenon was originally identified during studies conducted at the Hawthorne Works plant, where researchers found that workers improved their output when they were aware that their performance was being observed, regardless of any changes to their working conditions. The essence of the Hawthorne Effect lies in the intrinsic motivation to perform better when one knows they are being evaluated, leading to potential biases in research outcomes if not accounted for.

The other terms listed in the choices refer to different aspects of research and participant interactions. Demand characteristics involve cues that guide participants towards certain behaviors based on what they think the study entails. The Rosenthal Effect, similar to the Hawthorne Effect, pertains to the impact of expectations on participant performance. Experimenter bias refers to the influence researchers' expectations may have on the outcomes of the study. Collectively, understanding these concepts helps in designing better research methodologies and interpreting results accurately.